This invention relates to a radial-ply pneumatic tire of the open-torus type which is intended for use in combination with a specially designed rim.
The term "open-torus" refers to a tire, such as a conventional pneumatic tire, that has a toroidal shape that is open on its radially inner circumference. A conventional open-torus pneumatic tire has bead regions which are adapted to be mounted on a rim having axially opposed flanges that extend axially and radially outwardly. Typically, annular beads comprising metal wires or cables are used to restrain radially outwardly movement of the tire with respect to the rim upon which it is mounted. The flanges of a conventional rim do not restrain radially outward movement of the bead regions of a tire.
The modern radial-ply pneumatic tire is designed under standards promulgated by any number of individual organizations, including The Tire & Rim Association, Inc., The European Tyre & Rim Technical Organization, and The Japan Automobile Tire Manufacturers Association, et al. Under the standards promulgated by these organizations, which are quite similar, when a tire of a given size is being designed, it is designed for mounting on a "design rim", which is a rim having a specified configuration and width. "Design rim width" is the specific rim width assigned to each tire size and typically is equal to 70 percent of the specific tire's "section width". The section width is the width of the new tire, including 24-hour inflation growth and including normal sidewalls, but not including protective side ribs, bars, decorations or indicia. The "section height" of a tire is equal to the radial distance from the nominal rim diameter to the outside diameter of the tire at its equatorial plane.
The "aspect ratio" of a tire is the ratio of its section height to its section width. A "tire's design load" is the base or reference load assigned to a tire at a specific inflation pressure and service condition: and other load-pressure relationships applicable to the tire are based on that base or reference load. The terms "normal inflation pressure" and "normal load" as used herein refer respectively to the specific inflation pressure and load assigned by the appropriate standards organization for the design load as defined above for the service condition of the tire.
The conventional or modern radial-ply, open-torus pneumatic tire is now available in many configurations for many service conditions. It is generally recognized that the best overall performance is achieved with tire sidewalls in which the bead area adjacent the radially non-restraining flange is very rigid and gradually changes to a very flexible sidewall region before increased rigidity is encountered in the shoulder area of the tire, in which region the edges of the restrictive belt plies typically are located.
The tire structure described herein has flexible sidewalls without requiring stiffening elements adjacent the flanges. The flexibility of the sidewall enhances ride comfort yielding a soft feeling ride at inflation pressures equal or even higher than the typical modern radial tire.
Unlike conventional radial tires, the tire and rim combination of the invention described herein provides a means for retaining the beads in position on the rim in the event of a tire failure relating to deflation and loss air pressure. The sidewalls of the tire act as though hinged in proximity of the rim. The rim and tire design enables the rim to ride primarily over the deflated tire tread surface and provides a limited runflat capability. The flexible nature of sidewalls coupled with the rim permits avoidance of excessive abrasion. Conventional radial tires when run flat have the rim cutting into the sidewall, the bead unseating, and the road abrading the exterior surface of the sidewall. The invention claimed is an improvement over conventional radial tires.
While the tire structure disclosed herein departs significantly from commercially available conventional tires, through hindsight it may be seen to be reminiscent of tire development long since abandoned by the industry. Perhaps most significant of this abandoned prior art are those developments illustrated in British Patent No. 467 of C. H. Gray, dated 1913 and British Patent No. 29,639 to G. F. Fisher dated in the same year.